From single-celled bacteria to multicellular plants and animals, cells are the basic building blocks of every organism. They can be classified into two broad categories— prokaryotic and eukaryotic. Prokaryotic cells are relatively simple structures that lack membrane-bound organelles, barring a few exceptions. Their DNA is freely bundled in the center of a cell, a region called the nucleoid. In contrast, eukaryotic cells have a membrane-bound nucleus. Their overall structure is more complex and compartmentalized with specific organelles, like the mitochondria and endoplasmic reticulum. These organelles perform distinct functions but maintain internal communication that is essential for the cell's survival. Moreover, different eukaryotic organisms, such as plants and animals, vary in their exact cellular makeup. For example, a typical plant cell contains chloroplast, while animal cells do not. Thus, understanding the structural complexity and functionality of these cells is essential for learning about the biological world.